Variable camber propeller blade



y 4, 1965 J. c. MEDISCH ETAL 3,181,615

VARIABLE CAMBER PROPELLER BLADE Filed Aug. '7, 1963 2 Sheets-Sheet 1 INVENTORS J SEPH C. MEDIS H BY CLIFFORD B- WRIGHT wzgbw.

THEIR ATTOBNEY' M y 4, 1965 J. c. MEDISCH- ETAL 81,615

VARIABLE CAMBER PROPELLER BLADE Filed Aug. 7, 1963 2 Sheets-Sheet 2 LOW CAHBER I LEADING EDGE HIGH CAMBER INVENTORS JOSEPH C. HEDISCH CLIFFORD B. WRIGHT BY dlrzafl THEIR ATTORNEY 3,181,615 VARIABLE CAMBER PROPELLER BLADE Joseph C. Medisch and Clifford B. Wright, Indianapolis, Ind., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Aug. 7, 1963, Ser. No. 300,491 4 Claims. (Cl. 170--160.1)

the camber being automatically varied in accordance with the pitch position of the propeller blade.

Accodingly, among our objects are the provision of a variable camber propeller blade construction comprising a spar and a flap hingedly connected thereto throughout its length and constituting the trailing edge portion of the blade; the further provision of a variable camber pro- 2 peller blade construction of the aforesaid type including means for automatically varying the camber of the blade in accordance with the blade angle, or pitch position, thereof; and the still further provision of a variable camber propeller blade construction including a spar, a flap and a segmented spacer assembly for closing the gap between the spar and the flap in both the low and high camber positions of the flap, and wherein the flap is preloaded throughout its length by cam actuated mechanism to eliminate flap flutter and preclude air flow through the hinge connection between the flap and the spar.

The aforementioned and other objects are accomplished in the present invention by embodying integral clevis portions in the trailing edge of the spar which, together with complementary clevis portions on the flap form a hinge adapted to receive a hinge pin. The spacer is formed in a plurality of sections, and is supported by the hinge pin between the spar and the flap so as to close the gap between the spar and the flap in both the low and high camber positions of the flap.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a plan view, in elevation, of a variable camber propeller blade constructed according to th present invention, the blade being mounted in a hub socket.

FIGURE 2 is an enlarged fragmentary view, partly in section and partly in elevation, depicting the hinge joint between the flap and the spar.

FIGURE 3 is an enlarged fragmentary view taken'along 7 line 3-3 of FIGURE 1.

FIGURE 4 is an enlarged fragmentary sectional view taken along line 4--4 of FIGURE 1.

FIGURE 5 is a schematic view depicting the mode of operation of the variable camber blade of this invention.

' With reference to FIGURE 1, a variable pitch propeller is shown including a hub having a plurality of radially extending sockets, one of which is shown at 12.

A variable camber propeller blade 14- is journalled for rotation about its longitudinal axis in the hub socket 12 by suitable bearing means, not shown. The propeller lade 14 includes a root portion 16 which may enclose United States Patent 0 3,181,615 Patented May 4, 1965 a torque unit of known construction for rotating the entire propeller blade at its longitudinal axis to vary the pitch position thereof. The pitch changing and control mechanism for the propeller blade constitutes no part of this invention, but may be of the type disclosed in Bodem et al. Patent 2,986,220.

The variable camber propeller blade comprises a spar- 18 which, as shown in FIGURE 4, comprises a ribbed steel thrust member 20 that forms the blade shank, the root portion 16, the thrust face, and the leading edge of the propeller blade. A steel camber sheet 22 is copper brazed to the upstanding ribs of the thrust member 20 so as to form a thin, lightweight, high performance blade such as is well known in the art. A plurality of longitudinally spaced clevis portions 24 are machined as anbeam and has machined marginal edge surfaces 34 and 36 oriented at an angle of 10 to the aft rib 26. The flap 28 is completed by a pair of steel sheets 38 and 40 which are copper brazed to the supporting member 30 and roll welded to each other at the trailing edge 42, the cavity formed by the sheets 38, 40 and the supporting member 30 being filled with a low density polyurethane foam material. As shown in FIGURE 1, the spar 18 may be provided with an airfoil cuff portion 44 enclosing the shank of the propeller blade, which cuff may likewise be composed of a low density polyurethanefioam.

Four metal spacer sections 46, 48, 5t) and 52 are interposed and loosely mounted between the spar 18 and the flap 28, as shown in FIGURE 1. All of the spacer sections are apertured to receive and be supported by the hinge pin 58. As seen in FIGURE 4, the metal spacer section 48 has substantially flat machined marginal edge surfaces, the purpose of which will be pointed out hereinafter. It is to be understood that each of the spacers 46, 48, 50 and 52 is of similar construction, The inboard spacer 46, as shown in FIGURE 2, may have its exterior covered with rubber 54 to provide the necessary seal to accommodate the twisted profile of the spar and flap at the inboard end thereof, and all of the spacers have clevis portions 56 which are interposed between the clevis portions of the flap and the spar.

The spar, the flap and the spacer sections are hingedly interconnected by a longitudinally extending hinge pin 58 which extends throughout the length of the blade from the inboard end of the flap to the tip thereof. The shank of the spar 18 is formed with a support lug 60 which carries a thrust bearing assembly 62 for transferring the centrifugal loads imposed on the flap to the blade root 16.

The thrust bearing 62 is held in assembled relation with the support lug 60 by a bolt 64 having threaded engagement with the support member 30 of the flap 28. A hollow torque bar 68 encircles the shank of the bolt 64 and is rotatably journalled by the bearing 62. The upper end of the hollow torque bar 68 has a straight spline connection at 70 with the support member 30 of the flap 28, and the inboard end of the hollow torque bar 68 has a straight spline connection with an internally and externally straight splined indexing ring 72. A crank arm 74 is connected to the external straight splines of the indexing ring 72. The indexing ring 72 permits precise adjustment of the angular position of the flap 28 during assembly and enables aerodynamic matching of a spring;

,7 9 7:71 V. plurality of propeller blades in a multi-blade propeller assembly. The crank arm 74 carries a rollerv which rides in a cam track 78jattached' to the flangedjedgev of the" -As'seen part cularly in FIGURE 3,1 the {cam track 78 is formed with concentric grooves 80 and 82 of different radii, the grooves 86' and 82 being interconnected by over; the twist imparted to the fiap'in both the'low and ,jhighcarnber positions to preclude flutter is in the order an eccentric transition groove 84. Awasher 86 is interposed between the head of the bolt and the indexing ring 72, and the bolt is securely held'in position b'ya suitable external lock 88.

The profile, of the cam track.78 is correlated with pitch position of the propellerblade-so as to provide high camber at take off for maximum'thrust, andlo w camber during cruise'conditions." The roller 76 follows thefcarn track profile-during pitch adjustrnentofgtheblade relative to'its hub socket 12; Referring to FIG; 5,[ theaflap ZS-isShOWn 'inQthe high carriber positiri:in"full lines f' and injthe 'low' camber position inphantom lines; The

torque loads on the flap 28 are transferred to-the propeller hub throughthe hollow .torque'bar'68 and the crank arm74. "In both the highand low camber positions of the flap 28, ,a. seal is maintained at the hinge joint between,

the spar 18 and the fiap28 to prevent airleakage. Thus as showninFIGURE 4, when the'fiap 28 is in the low camber position'the"marginal edge. 34 of the support member '30" engages the spacer mernbers46,"48 50 and 52; throughout the length of the bladef Whenthe'fia'p mein ber 28 isinjthe high camber position E marginal edge 36 of the support member engagesfthe spacer. sections 46,48,50 and52. I

In the take oif position. of the propeller blade wherein p the pitch positionror blade angle, is ,relatively low the' flap 28' is rotated app'roximatelypll)?towards-gthe thrust 'face of the spacer 18 toobtainr ahigh camberfairfoil for" maximum takeoff thrust.v 'Asithe blade angle isincrease'd to the cruise position, the ca'm'rnechanism automatically rotatesthe flap to the low camber'position where it c om-f "plet'es the airfoil. shape of the blade to obtain optirnur'nf,

cruise efficiency. *Inboth 'the l'ow camber and. high camber positions of th'eflap. 28, theffiap is 'pr'eloa'ded throughout its length from the contoured cam track 78 Said: spar and saidflap,'- an 7 flap between high andlow; camber positions in. accordance of 1,fr'omthe thereof,

tip end of theyfiap ito theinboard end While the embodimentof'the invention asherein disclosed constitutes a preferred form, it. is to be understood that-other forms might be adopted, a

fWhat is claimed is as' follows:

1 Avariabldcamber propeller bladecoinprising, a

load supporting spar constitutinga leading edge and the 'rnajor portion of the thrust and camber surfaces of the *blade a trailing edge fiap'hingediy connected to said spar along. a subs antially straight line throughout its length, and spacer means looselysupporjted-by the-hinged connection between said fiapand. said spar for sealing the I gap between-said sparand said-flap infboth the low and high camber positions thereof;

T 2, A-variable camber propeller blade, comprising, a load supporting spar constituting. a leading edgeand the "major portion'ofthe thrust and camber surfaces of the blade, a trailing edge .fiap -hingedly connected to said spar throughout its-length, andia plurality of metal spacers loosely supported by the hinged connection between said zspar and said "fiapifor sealing thegap between said spar f and said flap in both-the highi'and low camber positions 1 thereof. I

3, The preparer bade set; forth in claim 2 wherein saidicsp'ar and {said flap have 'iinterpos'ed clevis portions :defining a straight line" hinge axis. throughout its length, and wherein said hinged connection includes an elongate hinge, pin extending through said interposed j-c levis'portions on'saids par and said flap. 1 V

' 4., A .variablefcamber propeller blade including a load supporting, spar constituting the leading edge and the majorportion of the thrust and camber surfaces of the blade; a trailing edge flap hingedly connected to'said spar throughout its .1ength, .gpace r. means interp'osed'between d'me'ans operableto rotate-said with the pitch position of said blade comprising a cam track,j.a.crank arm drivingly conhec'tedwith 'saidfiap and having affollower disposed Tinnsaid cain track; said 7 through the crank arm 74 by .twistingiit about tits longi; tudinal axis due'to abutment between one ofthe'mar'ginal.

edges34 or 36 of the fiap rnember 281=and the marginal edge surfaces offthe spacer sections 46; 48; 50-and 52. This preloading reduces flutter and maintains the requisite seal between the flapythe spacers and't'he spar to pre- V clude air flo w through the "hinge line/The hinge a'xis between the flap and the spar isast'i aightline soiasf'to facilitate angular movement of theflap relative- -to lthe 1 spar. During movement of-the flap between the high.

and low camber positions, "and viceflersa, that; is when the roller 76 is in the transition groove '84. of the cam; the. flap is not twisted, or preloaded whereas inthe opera;

I length from its tipjend to. its in board end to eliminate flapiflutt'er and said fiap-sea'lingly engaging said" spacer meansin'both 'its high and low camben positions so as V to closethe'g'apibetweensaid spar and said flap.

ating positions the flap is twisted'and acts as a torsionj,

, Frornthe wherein camber vvariationfis obtained by mechanically I V foregoing it isfapp arent-l that ine t-a ent invention provides a variablexcamber propeller bl'ade 6i changingfthe angle of the trailing portion," or. flap, of the. i

3 blade chord 'about-a longitudinal hinge axis. 7 Inja' typical V i propeller installation the camber is lincreased'from 25; i to ,75 with the resultingthrust increasez of. 24%. More drivingfconnectionbetween-said crank-arm and saidjflapi including a torque rod; and an *internally -.and V externally straight splined indexing ring whereby the angular posi-.

' tionof saidfflap canbe precisely adjusted toaerodynamically match a plurality'of' propeller blades, said cam track being contoured to twist said 'flap throughout its V- p I References Cited bylth'e Examiner "UNI-TED: STATESPATENTS 1,886,289:

JUL Us EL W ST, Primm fExamma}. V, 

1. A VARIABLE CAMBER PROPELLER BLADE COMPRISING, A LOAD SUPPORTING SPAR CONSTITUTING A LEADING EDGE AND THE MAJOR PORTION OF THE THRUST AND CHAMBER SURFACES OF THE BLADE, A TRAILING EDGE FLAP HINGEDLY CONNECTED TO SAID SPAR ALONG A SUBSTANTIALLY STRIGHT LINE THROUGHOUT ITS LENGTH, SAID SPACER MEANS LOSSELY SUPPORTED BY THE HINGED CONNECTION BETWEEN SAID FLAP AND SAID SPAR FOR SEALING THE GAP BETWEEN SAID SPAR AND SAID FLAP IN BOTH THE LOW AND HIGH CAMBER POSITIONS THEREOF. 